Paper with higher oil repellency

Abstract

This disclosure provides for a process for making an oil and grease resistant cellulosic material such as paper and paperboard, the process comprising applying a homogeneous aqueous dispersion of fluorochemical surface-modified nanoparticles to a cellulosic substrate to form a treated cellulosic substrate, and subsequently drying the treated cellulosic substrate to form an oil repellent cellulosic material. Fluorochemicals that can be used to modify the nanoparticles include fluoroalkylsilanes, ionic fluorochemicals, or fluorinated polyacrylate obtained by seeded emulsion polymerization of fluorinated acrylates on the nanoparticles. Paper, paperboard and cellulose fiber articles that have been modified by the disclosed processes have improved oil and grease resistance properties.

We claim: 
     
         1 . A process for making an oil repellent cellulosic material, the process comprising:
 a) applying a homogeneous aqueous dispersion of fluorochemical surface-modified nanoparticles to a cellulosic substrate to form a treated cellulosic substrate; and   b) drying the treated cellulosic substrate to form an oil repellent cellulosic material.   
     
     
         2 . The process of  claim 1 , wherein the fluorochemical comprises at least one fluoroalkylsilane, ionic fluorochemical, or fluorinated polyacrylate. 
     
     
         3 . The process of  claim 2 , wherein the at least one fluoroalkylsilane has the formula
   [F(CF 2 ) n CH 2 CH 2 ] m Si(OR) p ,   
       wherein:
 n is 2, 3, or 4; 
 m is 4-p; 
 p is 1, 2, or 3; and 
 R is a C 1 -C 6  hydrocarbyl or —C(O)R 1  wherein R 1  is independently a C 1 -C 6  hydrocarbyl. 
 
     
     
         4 . The process of  claim 2 , wherein the at least one ionic fluorochemical is selected from an amine, a polyamine, a quaternary ammonium salt, a cationic fluorochemical comprising azetidinium groups, or a combination thereof. 
     
     
         5 . The process of  claim 2 , wherein the at least one ionic fluorochemical is prepared from the reaction of an epihalohydrin with a compound of the formula:
   Z—(X) y —C(O)—NH[(CH 2 ) m —NH] n —C(O)—(X) y —Z,
   
       wherein
 Z in each occurrence is selected from an acyclic group C s F (2s+1)  wherein s is an integer from 3 to 20, and a cyclic group C t F (2t−1)  wherein t is an integer from 4 to 6; 
 X in each occurrence is selected from (CH 2 ) p  wherein p is an integer from 2 to 14, cycloaliphatic radicals, bridged cycloaliphatic radicals, —CH═CH—(CH 2 ) b —O—(CH 2 ) 2 —, —CH 2 —CH 2 —(CH 2 ) b —O—(CH 2 ) 2 —, —CH═CH—(CH 2 ) b —S—(CH 2 ) 2 —, —CH 2 —CH 2 —(CH 2 ) b —S—(CH 2 ) 2 — radicals, where b is zero or an integer of from 1 to 14, and —SO 2 —N(R)—(CH 2 ) q — radicals, wherein R is an alkyl radical containing from 1 to 6 carbon atoms and q is an integer of from 2 to 12; 
 y in each occurrence is 0 or 1; 
 m is an integer of from 2 to 6; and 
 n is an integer of from 2 to 100. 
 
     
     
         6 . The process of  claim 2 , wherein the ionic fluorochemicals are anionic compounds retained on the nanoparticles with an intermediate cationic polymer. 
     
     
         7 . The process of  claim 1 , wherein the fluorochemical surface-modified nanoparticles comprise non-fluorinated alkylsilyl moieties having the formula
   [H(CH 2 ) x ] y Si(O—) z ,
   
       wherein:
 x is an integer from 1 to 12; 
 y is 4-z; and 
 z is 1, 2, or 3. 
 
     
     
         8 . The process of  claim 1 , wherein the cellulosic substrate comprises a component selected from paper, paperboard, and cellulose fiber. 
     
     
         9 . The process of  claim 1 , wherein the fluorochemical surface-modified nanoparticles form a layered structure on the cellulosic substrate having a thickness of less than about 10,000 nanometers. 
     
     
         10 . The process of  claim 1 , wherein the nanoparticle comprises silica, titania, zirconia, layered magnesium silicate, aluminosilicate, natural clay, synthetic clay, polystyrene, styrene acrylonitrile (SAN), or combinations thereof. 
     
     
         11 . The process of  claim 1 , wherein the nanoparticle comprises at least one clay selected from smectites, kaolins, illites, chlorites, attapulgites, sepiolites, or combinations thereof. 
     
     
         12 . The process of  claim 1 , wherein the nanoparticle comprises montmorillonite, bentonite, pyrophyllite, hectorite, saponite, sauconite, nontronite, talc, beidellite, volchonskoite, vermiculite, kaolinite, dickite, halloysite, nacrite, antigorite, illite anauxite, indellite, chrysotile, bravaisite, suscovite, paragonite, biotite, corrensite, penninite, donbassite, sudoite, pennine, sepiolite, polygorskyte, clinochlore, chamosite, nimite, pennantite muscovite, phlogopite, synthetic hectorite, or phengite. 
     
     
         13 . The process of  claim 1 , wherein the fluorochemical surface-modified nanoparticles are present in the aqueous dispersion at a concentration from about 0.01% to about 50% by weight of the total composition. 
     
     
         14 . The process of  claim 1 , wherein the homogeneous aqueous dispersion further comprises an emulsion polymer or a fluorinated resin emulsion. 
     
     
         15 . The process of  claim 1 , wherein the aqueous dispersion of fluorochemical surface-modified nanoparticles further comprises a wetting agent, an anti-soil agent, an anti-stain agent, a fluorochemical resin, a surfactant, a silicone, an optical brightener, an antibacterial component, an anti-oxidant stabilizer, a coloring agent, a light stabilizer, a UV absorber, starch, polyvinyl alcohol, a retention aid, a wet strength aid, an alkylated inorganic nanoparticle having no fluorine content. or any combination thereof. 
     
     
         16 . A paper or paperboard made according to the process of  claim 1 . 
     
     
         17 . An article comprising an oil repellent cellulosic material made by a process comprising:
 a) applying a homogeneous aqueous dispersion of fluorochemical surface-modified nanoparticles to a cellulosic substrate to form a treated cellulosic substrate; and   b) drying the treated cellulosic substrate to form an oil repellent cellulosic material.   
     
     
         18 . The article of  claim 17 , wherein the concentration of fluorine on the oil repellent cellulosic material is either from about 10 ppm to about 500 ppm by weight (w/w), or from about 0.0001% to about 0.10% by weight. 
     
     
         19 . The article of  claim 17 , wherein the fluorochemical surface-modified nanoparticles are present on the oil repellent cellulosic material at a concentration of either from about 0.01% to about 2.0% by weight, or from about 0.01 to about 3 grams per square meter (g/m 2 ) of surface area of the oil repellent cellulosic material. 
     
     
         20 . A paper or paperboard treated with a homogeneous aqueous dispersion comprising fluorochemical surface-modified nanoparticles to form an oil-repellent paper or paperboard.